The invention relates to improved apparatus for reducing lumps of material to particle and granular form and, while the invention has uses in various manufacturing and mining environments, the invention will be particularly described herein with relation to use in foundries for recovering sand from molding operations and treating the sand for reuse.
In order to economically utilize the no-bake or air-set molding processes it is essential to reclaim the sand for reuse. Several methods are now used to granulate the lumps and recondition the sand. Typical methods now used include:
1. Breaking the lumps into granules by utilizing a centrifugal throwing wheel which propels particles of shot against the lumps,
2. A vibratory tub device, or a vibrating conveyor, for breaking up of lumps,
3. A sand muller which is provided with perforated holes in the bottom thereof through which the crushed sand passes,
4. A rotating propeller or paddle type mechanism is used for crushing the lumps.
All of the foregoing mentioned methods work to a greater or lesser degree. Type 1 is probably the best system in that the lumps are bombarded with millions of particles of shot, such as steel balls and the like, and this multiple impact system breaks the large lumps down into individual pieces of sand and the high velocity of the shot also removes a portion of the binder which is used during the mold forming operation to hold the grains of sand together. A disadvantage of this system is the large expense for low capacity operations. An additional disadvantage is that it will not handle large lumps, on the order of 1 foot to 3 feet, in an easy and speedy manner.
Type 2 does a reasonably good job in reducing the sand lumps to individual sand particles; however, the vibratory action does little to remove the binder from the sand particles and a greater disadvantage is the extreme wear on the tub or vibrating parts which become quickly abraded by the sand particles.
Type 3 also does little to remove the binder from the sand particles and is quite inefficient in reducing the sand to individual sand grains because the sand is forced through relatively large holes in a perforated bottom plate or pan.
Type 4 also does little to remove the binder from the sand particles and is inefficient in reducing sand to individual grains. Further, wear on the crusher blades or propellers is very high.
The present invention, in addition to overcoming undesirable features of the prior art includes the following particularly desirable features:
1. The invention provides a relatively inexpensive unit, as compared to prior art apparatus, that will reduce lumps of sand or other minerals to a granular or particulate form in a very efficient manner.
2. The main abrading element of the present invention is comprised of a highly wear resistant material, such as bonded abrasive grinding wheels and the like, which is very efficient, long lasting, and readily replaceable.
3. The improved apparatus is very efficient in reducing lumps of sand into individual sand particles or grains.
4. The present apparatus is readily suitable for handling large cubes or irregular lumps of material having dimensions on the order of 1 to 3 feet.
5. As the lumps are reduced to particle or granular size the particles form a cushion between a bonded abrasive grinding medium and the lumps which minimizes wear of the grinding medium.